<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="../../js/vue.js"></script>
</head>

<body>
    <div id="app">
        <mycom></mycom>
    </div>
</body>
<template id="aa">
    <div>
        {{num}}
        <button @click="add">+</button>
    </div>
</template>
<script>
    Vue.component("mycom", {
        data() {
            return {
                num: 10
            }
        },
        template: "#aa",
        methods: {
            add() {
                this.num++;
            }
        }
    })
    new Vue({
        el: "#app"
    })
</script>

</html>